1. Field Of The Invention
The present invention is directed to a communications device, such as, for example, a modem and a method for enabling data communication, and in particular, to an apparatus and method that detects various communication configurations and selects an appropriate communication configuration to establish a communication link.
2. Discussion Of Background And Other Information
Traditionally, data communication devices, such as, for example, modems (both analog and digital), have been employed over public switched telephone networks (PSTN) to transmit data between a first location and a second location. Such modems operate within a conventional voice band (e.g., approximately 0 through 4 kHz bandwidth) of the PSTN. Early modems transmitted data over the PSTN at a speed of approximately 300 bits per second (bps), or less. Over time, and with the increased popularity of the Internet, faster communication schemes (e.g., modems) were demanded and developed. Currently, the fastest analog modem available (referred to as an ITU-T V.34 modem, as defined by the International Telecommunication Union (ITU)), transmits data at a rate of approximately 33,600 bps under ideal conditions. These modems continue to exchange data within the approximate 4 kHz bandwidth of the PSTN.
It is not uncommon to transfer data files that are several megabytes (MB) in size. A modem that operates utilizing the V.34 modulation requires a long time to transfer such a file. As a result, a need has developed for even faster modems.
Accordingly, many new communication methods are being proposed and/or developed to transmit data on the local twisted wire pair that uses the spectrum above the traditional 4 kHz band. For example, various xe2x80x9cflavorsxe2x80x9d (variations) of digital subscriber line (DSL) modems have been/are being developed, such as, but not limited to, for example, DSL, ADSL, VDSL, HDSL and SDSL (the collection of which is generally referred to as xDSL). Several of the various xDSL schemes permit simultaneous communication on a single twisted pair in the voice band and the band above the voice band. Each xDSL variation employs a different communication scheme, resulting in different upstream and/or downstream transfer speeds, and utilize differing frequency bands of the twisted pair communication channel. In addition, some xDSL variations require filters including low pass filters, high pass filters and combinations of filters that are sometimes referred to as xe2x80x9csplittersxe2x80x9d, which may differ between the installations. The filters separate the frequency band that carries voice band communication from the frequency band above the voice band carrying data communication. The line environments surrounding the xDSL data communication schemes, such as, for example, their ability to co-exist with a conventional analog modem that communicates within the conventional voice band (e.g., 0-4 kHz bandwidth), differences in central office equipment, quality of the line, etc., are numerous, differ significantly, and are complicated. Accordingly, it is essential to be able to determine the capabilities of the communication channel in addition to being able to determine the capabilities of the communication equipment in order to establish an optimum and non-interfering communication link.
Conventional start-up sequences (such as, for example, V.8 and/or V.8bis protocols, as established by the ITU-T), as implemented by, for example, V.34 modems, use a sequence of bits transmitted from each modem to identify and negotiate the varying equipment capabilities, such as the modulation scheme employed, protocol, etc. These startup sequences are applicable only to the conventional voice band communication methods. These conventional startup sequences do not test (or disclose) the constitution and/or condition of the communication channel.
However, for xDSL modems, line condition information, such as, for example, frequency characteristics, noise characteristics, presence or absence of a splitter, etc., is useful at the time that two modems are negotiating prior to connecting to each other, if the communications link is to be successfully established.
Voice band line probing techniques are known in the art and can be used to determine voice band line condition information. Such techniques have been used effectively to optimize a given modulation method, such as, for example, V.34. In a set of devices with multiple modulation methods, V.8 or V.8bis has been used to negotiate and then select a particular modulation, and after that modulation initiation sequence has started, line probing techniques are used to receive some indication of the condition of the communication channel. If it is determined at that point that a given communication channel could not effectively support a chosen modulation method, time consuming heuristic (i.e., self-learning) fallback techniques are employed by the prior art to try and find a modulation method that works.
Accordingly, what is required to establish an improved communication link is a method to observe (or examine) the line conditions before attempting to select the most appropriate communication method. Thus, while techniques have been established to increase the data rate for a given modulation, the prior art does not provide a method for using channel information to aid in the selection of the communication method.
Unfortunately, in the current state of the art, capability negotiations occur without knowledge of the prevailing channel configuration. Explicit knowledge of spectrum, splitting, etc. is vital to the selection of the appropriate communication mechanism (modulation) decision process.
Based on the foregoing, the overall purpose of the present invention is to develop a communication method, modem device and a data communication system that detects various configurations, capabilities and limitations of a communication channel and associated equipment in order to determine a specific (xDSL) communication standard appropriate for the existing line conditions. To accomplish this goal, the invention employs several individual techniques as a system.
According to one aspect of the present invention, a method and apparatus are provided to negotiate between modems that embody a multiple (plural) communication methods (e.g., DSL standards), so as to select a single common communication standard to be used for a communication session. A communication control section executes a handshake procedure (protocol) in a negotiation channel to obtain information concerning high speed data communication, including type identification information of xDSL used in the communication exchange. A communication standard refers to any type of standard, whether defacto, proprietary, or issued by an industry or government body.
In another aspect of the instant invention, a method is provided for determining characteristics of the communication channel between a central communication system and a remote communication system by using an examination signal. The examination signal detects impairments, such as, but not limited to, frequency rolloff and noise, that are identified and disclosed between the central system and the remote systems. Information pertaining to the quality of the communication channel enables the present invention to make a more informed decision concerning the selection of the subsequent communication standard. (e.g., whether to use CDSL instead of ADSL, or use CDSL instead of VDSL.)
In another aspect, the invention provides a method and apparatus to determine the presence of equipment used to split frequency bands. In many cases, the presence of such equipment is necessary to provide communication in the frequency above the voice band. The lack of such splitting equipment may necessitate the use of different communication methods. The present invention includes a method for detecting the presence of such splitters that is non-intrusive, so as not to interfere with any communication (such as, for example, a voice communication or analog data communication) that may be concurrently using the voice band.
In another aspect of the invention, a fallback procedure to a traditional voice band communication method is provided if it is determined that a high speed band communication is not possible. A notification signal (such as, for example, a spread processed signal) is transmitted within the conventional voice band that is received by a first communication control section. The notification signal includes an identification signal that indicates the capability for performing data communication within the conventional voice band.
In addition, the notification signal also determines whether the communication equipment is capable of a high speed communication, even though the communication channel is currently not capable of high speed communication. This permits, for example, a user to purchase a high speed data communications device (e.g., modem), and install the device, at which point, the central office will automatically detect the installation of the high speed communication device (at the user""s location) and initiate an on-line procedure that enables the user at the remote location to order a high speed communication channel for the modem.
According to another feature of the instant invention, the notification signal that is transmitted in the voice band (to indicate that a high speed data communication can take place above the voice band) is selected so as not to interfere (disrupt) with a conventional communication (e.g., voice communication or analog data communication) that may be taking place in the voice band at the same time that a high data speed communication session is to be initiated. The notification signal, may be, for example, a spread spectrum signal that is generated with a pseudo random number sequence. Alternatively, other spread spectrum techniques that cause the transmission energy to be evenly spread throughout the voice band may be employed.
According to another aspect of the invention, an end user-to-end user communication, such as, for example, the exchange (transmission) of a user name, password, etc., may be initiated prior to the completion of the communication channel testing (e.g., line probing) and exchange of high speed communication capability, via a user clear channel. Previously, communications systems required a lengthy training (or startup) time before any end user-to-end user data could be communicated. The present invention enables a user communication path to be simultaneously established while the testing and negotiation (of the channel and communication method) used for the high speed communication is taking place.
The combination of all of the various aspects of the invention provides a method and apparatus for effectively and efficiently performing an audit of the communication channel and installed equipment to select the most appropriate communication method. System designers, installers, and providers are also able to set various parameters that are considered by the invention during the negotiation process to effectively define the meaning of xe2x80x9cmost appropriate means of communicationxe2x80x9d.
According to the present invention, the determination of a possible high speed communication, exchange and selection of the supported capabilities for a high speed data communication, and examination of the communication line characteristics can be concurrently (simultaneously) executed, thus enabling the immediate shifting to a handshake protocol corresponding to the determined data communication procedure.
The invention may be included in both sides of the communication channel for optimum negotiation. However, according to an advantage of the present invention, only one side of the communication channel may incorporate (contain) the invention. Still further, one side may only partially implement the present invention. Such configurations will be accurately reported to the communication systems, and, if appropriate, the communication systems can fallback to legacy (e.g., analog) communication methods if the communication system supports such method.
Further, the instant invention does not need to be embodied in the actual high speed communication devices themselves. The invention can be implemented in intelligent switches that terminate and/or segment the communication channel. This allows a communication system to use various communication standards implemented in separate devices (or modems) that can be correctly assigned (on a xe2x80x9cas neededxe2x80x9d basis) through explicit negotiation of the capabilities and desires of the central system and the remote communication system.
According to an object of the instant invention, a method for selecting a communication standard from among a plurality of communication standards, comprises auditing a condition of a communication channel, and selecting the communication standard based upon the audited condition of the communication channel and a capability of each of the plurality of communication standards. Auditing of the condition of the communication channel comprises issuing a first signal over the communication channel in the signal, receiving an estimate of the effects of the communication channel, and then selecting the communication standard in response to the received estimate. Selecting of the communication standard comprises selecting one xDSL modem standard from among a plurality of xDSL modem standards.
According to an advantage of the present invention, communication standard capability information and/or user data may be issued at substantially the same time as the condition of the communication channel is audited.
A further advantage of the present invention resides in its ability to determine whether a communication channel includes a splitter.
Another object of the current invention pertains to a communications device for exchanging data, comprising a first communication device that at least one of transmits and receives negotiation information relating to communication standards over a communication channel, and a second communication device that at least one of transmits and receives examination information (such as, for example, a plurality of signals in different frequency bands) over the communication channel to determine line characteristics of the communication channel.
According to an advantage of the invention, the negotiation information and the examination information are exchanged in a substantially concurrent time period. Alternatively, the negotiation information and the examination information are exchanged in different time periods.
According to a feature of the invention, the communication device exchanges the examination information over the communication channel in a predetermined frequency band. Further, the communication device may exchange an optional examination signal in a second frequency band.
Another object of the instant invention resides in a communications device, comprising a first communication device that exchanges negotiation information between two locations, and a second communication device that at least one of transmits and receives user data. The negotiation information relates to a communication standard, such as, for example, ADSL, CDSL, HDSL, etc. and/or characteristics of a communication channel.
According to another object of the invention, a communications device is disclosed for exchanging data, comprising a first communication device that exchanges negotiation information related to a predetermined data communication, and a second communication device that exchanges a fallback notification signal over a predetermined data communication band, in which the fallback notification signal is used to indicate an availability of the second predetermined communication band.
According to an advantage of the invention, the second predetermined data communication band comprises a voice band. A voice band communication device may be used when the first communication band is unusable.
According to an advantage of the invention, the negotiation information and the fallback notification signal may be exchanged in a substantially concurrent time period, or in different time periods.
According to another advantage of the invention, the fallback negotiation signal (which may be, for example, a spread spectrum signal) does not interfere with any communication in the voice band.
Another object of the current invention pertains to a method for exchanging data between an initiation location and a responding location. According to this method, the method determines whether a predetermined signal is detected by the responding location. Fallback procedures (e.g., voice band procedures) are initiated if the predetermined signal is not detected by the responding location. On the other hand, if the predetermined signal is detected, negotiation information is exchanged between the initiating location and the responding location to establish capabilities of the initiating location and the responding location. Channel information is received by one of the initiating location and the responding location, and an appropriate communication standard is selected utilizing at least one of the exchanged negotiation information and received channel information, to establish a communication link.
According to a feature of the invention, the method further comprises analyzing the received channel information, and using the analyzed information in conjunction with the at least one of the exchanged negotiation information and received channel information to select the appropriate communication standard.
According to another feature of the invention, user data may be exchanged between the initiating location and the responding location while the xe2x80x9cinitializingxe2x80x9d procedure is taking place.
According to another object of the instant invention, a data communications device (such as, for example, a modem) is disclosed that includes means for determining line characteristics of a communication channel, and means for initiating a high speed data communication over the communication channel, based upon the line characteristics of the communication channel determined by the determining means. A notification signal may be exchanged over the communication channel in a voice band, in which the notification signal indicates high speed data communication capabilities of the communications device.
According to a feature of the invention, the high speed data communication channel utilizes a frequency band higher than the voice band.
According to an advantage of the invention, means for determining a communication standard of the communication device may be included, so that a high speed data communication can be initiated in accordance with the determined communication standard and the determined line characteristics.
According to another advantage of the invention, means for performing a data communication over the communication channel in a voice band may be provided when the determining means determines that the communication channel does not support a high speed data communication.
A still further advantage of the invention is the inclusion of means for determining a presence of a splitter in the communication channel, in order to optimize the performance of a communication standard.
Another object of the instant invention pertains to a method for enabling data communication by detecting a presence of a splitter in a communication channel, and then determining whether high speed communication is available. The presence of a splitter may be detected using a signal that does not adversely interfere with a voice band communication.
The present disclosure relates to subject matter contained in Japanese Patent Application No. HEI 10-15057, filed on Jan. 9, 1998, which is expressly incorporated herein by reference in its entirety.